Preheat oven to 350. Make cake by beating butter and brown sugar together with an electric mixer until smooth. Add eggs, vanilla, ginger and salt and beat well. Gradually mix in flour until smooth. Mix 3/4 cup diced dried cranberries and white chocolate into the batter by hand. Pour batter into a well greased 9x13 baking pan. Use a spatula to spread the batter evenly across the pan. Bake for 35 to 40 minutes or until cake is light brown on the edges. Allow cake to cool.
Make frosting by combining softened cream cheese, 3 cups powdered sugar, lemon juice and vanilla extract in a medium bowl with an electric mixer until smooth. When the cake has cooled, use a spatula to spread frosting over the top of the cake.
Sprinkle 1/4 cup of diced cranberries over the frosting on the cake.
Whisk together 1/2 cup powdered sugar, 1 tablespoon milk, and shortening. Drizzle icing over the cranberries in a sweeping motion or use a pastry bag with a fine tip to drizzle frosting across the top of the cake.
Allow cake to sit for several hours, then slice the cake lengthwise (the long way) through the middle. Slice the cake across the width three times making a total of eight rectangular slices. Slice each of those rectangles diagonally creating 16 triangular slices. Makes 16 bars.